2025/06/08 by Martinelli, Filippo, Anton N. Vetlugin, Shuyu Dong +10
Computer Science · Physics and Astronomy · Materials Science · #Quantum Information and Cryptography #Mechanical and Optical Resonators #Diamond and Carbon-based Materials Research
paper · pdf · doi:10.48550/arxiv.2506.07029
We report the realization of inline quantum measurements with waveguide-integrated superconducting nanowire single-photon detectors (SNSPDs). To suppress parasitic scattering at detector terminations, while ensuring compatibility with standard photonic substrates and cryogenic operation, we developed a photonic bound states in the continuum (BIC) platform based on etchless polymer waveguides. We show BIC-coupled inline detectors with on-chip efficiency exceeding 80%, recovery time of less than 2 ns, and intrinsic jitter of less than 70 ps. As a proof of principle, we implement Hanbury Brown and Twiss interferometry and photon number resolution with two collinear detectors within a footprint of 60 ⋅ 6 μm2. The concept of inline quantum measurements could be further developed to support more complex circuit functionalities, such as higher-order correlation measurements, quantum state tomography, and multi-photon subtraction, within a compact architecture.